"make altinstall" installs "2to3", "pydoc3" and "idle3" without version specific names.
This was at least a deliberate decision in the case of 2to3, but there doesn't appear to be any reason not to use a properly qualified version suffix on the pydoc and idle executables.

Attaching a patch that should fix it. The delegation of the links to the Makefile is not ideal, but I don't see how to easily do it otherwise.
While this is reviewed, deferring as it should not block beta2.